Pug mill mixer having improved aggregate circulating means



Nov. 25, 1958 w. M. MADSEN PUG MILL MIXER HAVING IMPROVED AGGREGATECIRCULATING MEANS 2 Sheets-Sheet 1 Filed Nov. 28, 1952 MM NN W i?flfMasa-A INVENTOR.

Nov. 25, 1958 w. M. MADSEN PUG MILL MIXER HAVING IMPROVED AGGREGATECIRCULATING MEANS 2 Sheets-Sheet 2 Filed Nov. 28, 1952 W44 75? MMOSE/K,

INVEN TOR.

United States Patent I O PUG MILL MIXER HAVING IMPROVED AGGRE- GATECIRCULATING MEANS Walter M. Madsen, Alhambra, Califi, assignor, by mesneassignments, to Baldwin-Lima-Hamilton Corporation, Philadelphia, Pa., acorporation of Pennsylvania Application November 28, 1952, Serial No.322,859

9 Claims. (Cl. 259-146) This invention relates generally to a method andapparatus for mixing'materials and relates more particularly to suchmethod and apparatus to mixing machines of the pug mill type and methodof mixing materials therein.

,While the invention has particular utility in connection with a methodand equipment or apparatus for mixing materials for road constructionand the like and is shownanddescribed in connection therewith, it is tobe understood that itis not confined thereto.

.It is common practice at the present time to produce a paving materialby mixing a mineral aggregate, which consists of sand, gravel, granite,or rock pieces of different sizes, with a binding material, such as abituminous or asphalt material. It is quite essential to the productionof a material which will make a good road to take care during the mixingoperation that each mineral aggregate piece will be coated with bindermaterial. In this Way the paving material, when properly laid on theroadbed, will produce a road which produces a better traveling surfaceand which has a longer life than it would have if the mixture of mineralaggregate and binder were not as thorough as pointed out above.

ItIis, therefore, an object of the present invention to provide methodand apparatus whereby the mineral aggregate and binder is thoroughlymixed.

It is another object of the invention to provide method and apparatus ofthis character whereby the mixing of the aggregate and binder isgreatly. facilitated.

It is still another object'of the invention to provide method andapparatus of this character whereby there is better distribution andcirculation of material within the mixer body.

A further object of the invention is to provide a method and apparatusof thischaracter to provide constant overthe-top distribution of rockand sandand the like and the binder and thus eliminate concentration oflarge or small sizes of solid materials in pockets within the mill.

A still further. object of the invention is to provide a method andapparatus of this character for transporting the material to voidscreated at the end of the mill by action of the mixing arms. 7

Other objects and advantages of the invention Will be brought out in thefollowing part of the specification.

Referring to the drawings, which are for illustrative purposes only: 7

Fig. .1 is a partial longitudinal section of apparatus embodying thepresent invention;

Fig. 2 is. a sectional view taken on line 22 of Fig. l; and

Fig. 3 is an end view of the apparatus.

Referring more particularly to the drawings, there is Patented Nov-25,1958 19 which is closed by a longitudinally sliding door 20 received inchannel-like tracks 21. The door is adapted to be moved to a positionwhereat the opening 19 is uncovered so that material which has beenmixed in the body may be discharged therefrom.

There is means for mixing materials within the body and this meanscomprises a pair of shafts 24 which extend longitudinally of the body 11and which are supported adjacent the ends by suitable bearings 25, saidshafts being simultaneously rotated by means of gears 26, 27 and 28, thegears 27 and 28 being secured to the respective shafts 24 and beingmeshed with each other. The gear 26 is connected by any suitable means,not shown, to a source of power, also not shown.

The shafts 24 are on axes from which the radii of the bottom portions 18extend as bestshown in Fig. 2, and

each shaft is provided with a plurality of paddles 30 connected with theshafts 24' by means of arms 31. The paddles are arranged symmetricrelative to a plane through the line 2-2, the paddles on one side ofsaid plane being angularly disposedin one direction, while the paddleson the opposite side of this plane are angularly disposed in theopposite direction. These paddles are arranged so that the materials 'inthe mixer body are agitated and are moved through cylindrical or spiralpaths from the ends of said body. This material moves toward the centralportion of the mixer body and is carried to the upper central portionthereof, as indicated by the dotted line 33 in Fig. l. The liquid bindermaterial is applied at this point and is sprayed onto the materialthrough openings 34 in a tubular shaft or spray pipe 36 which extendslongitudinally of the mixer body which extends along, or substantiallyalong, the plane AA, Fig. 2. This shaft 36 is substantially parallel tothe shafts 24 and is located in the upper portion of the mixer bodyabove the plane of said shafts 24.

The shaft 36 is rotatablymounted in bearings 40 in end walls 41 of anupper casing or body section, indicated generally at 43. One end of theshaft 36 is connected to the outlet 44 of a pump 45 of a pressureinjection system which is indicated generally at 46. The pump 45 isdriven by any suitable means such as an electric motor 47 through a belt48. Liquid asphalt or the like enters the injection system through aninlet conduit 49 and the shaft 36 is connected to the outlet of saidpump 45 by means of a suitable swivel coupling 50, such couplings beingwell known in the art.

The spray pipe or shaft 36 is provided with a helical flight conveyor 52which has hardened edges and the conveyor is parallel to the shafts 24and positioned to operate in the peak of the material built up by thepaddles in the central region of the mixer body. The flight may be ofany suitable length and may be from approximately one-half to two-thirdsthe length of the mixer with the flight positioned in the center anequal distance from each end of the mill of the body. It is to beunderstood, of course, that other lengths for the flight may be selecteddepending on the installation.

The flight is adapted to be operated first in one direction and then inthe other and is actuated by any suitable source of power such as anelectric motor 55. The motor is provided with a sprocket 56 and theshaft 36 is provided with a sprocket 57 with a chain connection 58therebetween. The motor 55 is adapted to be con nected to any suitablesource of electric current and is provided with a reversing switchmechanism 55a which may be of any suitable well-known type so that themotor will operate a predetermined number of revolutions in onedirection and then operate a predetermined numberof revolutions in theopposite direction to correspondingly actuate the shaft 36.

It 'is to be understood, of course, that other power means may beprovided for driving the shaft 36 and such power means suitablycontrolled to eifectreversing movement of the shaft 36. Means foreffecting reversal of the shaft rotation may be provided between thesource of power andsaid shaft.

When the apparatus is in operation, the shafts 24 rotate, one in a.clockwise direction and :the .other counterclockwise, and the materialin the mixer body is mixed and caused to assume a peak or-ridge positionin the center of the mill parallel to the shafts above the height of themixer arms. Thescrew conveyor 52 operates in the upper portion of thisaccumulated material and, as it rotates in one direction, moves saidmaterial toward one end of the mixer body, and, as it rotates in theopposite direction, moves said material to the opposite'end ofsaid body.Thus the material within the mixer body -is caused to circulate or movefrom the end toward the center and upwards and thence to be movedfrom-the top ofthe pile toward the ends of said body.

During the mixing action, the binder, which comprises liquid asphaltorthe like, is discharged from the openings of the-shaft 36 and mixedwith the aggregate.

An alternative arrangement for causing the aggregate along the upperridge to be moved toward the ends of the mixerbody'may comprise ahelical .fiight divided in the middle and formed right-hand on one sideand left-hand on the opposite side. With this arrangement, the shaft 36may be constantly rotated in one direction.

Another alternative arrangement for moving the ma terial at the top ofthe pile formed in the body by the paddles 30 is to provide paddles onthe shaft 36 which would operate to move the materials in one directionupon rotation of said shaft in such a direction and move the material inthe opposite direction upon reverse rotation of the shaft 36. Further, apaddle arrangement may be provided whereby said paddles cause movementof the material at one side of the longitudinal center of the bodytoward one end of said body and the material at the opposite side of thelongitudinal center of the body toward the opposite end. With thesearrangements the shaft 36 would be operated continuously in onedirection as in the case of the divided helical flight conveyorarrangement above described.

There is another arrangement wherein the material in the mixer body maybe moved toward one endby the paddles on the shafts 24 and a part, atleast, of the upper portion of the mass of material moved in theopposite direction by the moving means disposed above the plane of theshafts 24. This will effect a more thorough mixing of the aggregate andbinder materials.

A V-shaped bafile, indicated generally at 60, may be provided over thehelical flight, as best shown in Figs. 2 and 3. This baffle has its apexat the top and is provided with end flanges 61 which are secured by.bolts 62 or other suitable means to the ends of the section 43. Thebafile 60 serves to divide the stream of aggregate discharged into themixing machine from a hopper 64 and may also serve as a cover of saidflight.

I claim:

1. A method of producing paving material, which includes the steps of:mixing an aggregate and moving two bodies thereof toward each other sothat said bodies merge together and move upward; moving materialrfromthe upper part of the merged bodies, first in one direction and then theother, the directions of movement being opposite the directionofmovement of said contiguous bodies; and applying a liquid bindingmaterial to the aggregate.

2. In apparatus for mixing paving material, the combination of: mixingmeans for mixing an aggregate so that same is divided into twocontiguous bodies which move in separate spiral paths which mergetogether and move .upward alongthecontiguous parts of said bodies; meansfor moving the material of said bodies outward in directions oppositethe direction said material moved in said paths; and liquid applyingmeans for applying, under pressure, a liquid binding material in streamsto said aggregate during the aforesaid mixing operation at the upperpart of said contiguous parts of said bodies, where said material ofeach body is moved outwardly, said mixing action being continued tothoroughly coat said aggregate.

3. In apparatus for mixing paving material; mixing means for mixing anaggregate so that same is divided into two contiguous bodies which movein separate spiral paths which merge together and move upward along thecontiguous parts of said bodies; means for positively moving thematerial of said bodies in directions opposite the directions saidmaterial moved in said paths; and liquid applying means for applying,under pressure, a liquid binding material to said aggregate during theaforesaid mixing operation at the upper part-of said contiguous partsofsaid bodies, where said material of each body is moved outwardly, saidmixing action being continued to thoroughly coat said aggregate.

4. In apparatus for mixing paving material: a mixer body; mixing meansin said body for mixing an aggregate so that same is moved in two bodiesin separate paths which merge together and move upward along thecontiguous parts of said bodies; material moving means for moving thematerial of said bodies outward and out of contact when the upper end oftheir merged and contiguous travel is reached; and liquid applying meansfor applying, under suflicient pressure to obtain penetration'into saidaggregate, a liquid binding material in streams to said aggregate duringthe aforesaid mixing operation at the upper part of said contiguousparts of said bodies.

5. In apparatus for mixing paving material and the like: a mixer body;mixing means in said body for mixing an aggregate therein and movingsame inwardly and upwardly into a body of mixed material; materialmoving means for moving material at the top of said body of materialoutwardly; and liquid applying means for applying a binding material tosaid aggregate.

6. In apparatus for mixing paving material and the like: a mixer body;agitation and mixing means in said body extending longitudinallythereof, said agitating and mixing means being adapted to mix anaggregate in said body and move same from their ends to a central upperregion of said body; and material moving means extending longitudinallyof said body and moving material from the upper central region of themixer body toward the respective ends thereof.

7. The invention defined by claim 6 including actuating means foroperating the material moving means; and means for reversing saidactuating means.

8. In apparatus for mixing paving material and the like: a mixed body; apair of shafts in said body extending longitudinally thereof, saidshafts being spaced laterally apart in substantially the same horizontalplane; mixing and agitating means for each of said shafts, said mixingand agitating means being arranged on said shafts so as to moveaggregate material in said body from the ends thereof in paths so thatsaid material is moved toward the center and upper region of the body; atubular perforate shaft above the plane of the first mentioned shafts,said tubular shaft being rotatably mounted and adapted to receivebinding material therein for discharge through the perforations thereof;material moving means on said hollow shaft adapted to move material fromthe upper central region of said body toward the respective endsthereof; power means for rotating said tubular shaft; andmeans-forcausing said 5 power means to operate said shaft, first in one directionand then in the opposite direction.

9. A method of mixing paving material and the like in a mixed body,comprising the steps of: mixing an aggregate in said body and movingsame from the ends toward the center thereof and upwardly; andsimultaneously moving material from the upper part of the aggregate atthe central region of the mixer body toward the respective ends of saidbody.

References Cited in the file of this patent UNITED STATES PATENTS WeberAug. 24, 1920 Skirvin Jan. 6, 1931 Forster Apr. 26, 1932 Madsen Jan. 8,1935 Marshall Apr. 8, 1941 West Oct. 2, 1951 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 2;86l/786 November 25, 1958 WalterM. Madsen It is herebjr certified that error appears in the-printedspecification of the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 4, line 60, and column 5, line 4, for "mixed", in eachoccurrence, read mixer a Signed and sealed this 10th day of March 1959.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner ofPatents

